FIG. 1 shows a conventional athletic shoe 100. Shoe 100 includes an upper 102 and a sole structure 104. The upper 102, which may include a Strobel or other lasting element (not shown), defines a foot-receiving chamber that may be accessed through opening 106. The upper 102 provides a covering for a wearer's foot and securely receives and positions the foot with respect to the sole structure 104. The sole structure 104 may be secured to a lower portion of the upper 102 and positioned between the foot and the ground when the shoe 100 is in use. In addition to attenuating ground reaction forces, the sole structure 104 may provide traction and help control foot motion, such as pronation.
The sole structure 104 may have a layered configuration that includes a resilient midsole 108 (e.g., formed, at least in part, from a polymer foam material) and a ground-contacting outsole 110 that provides both abrasion-resistance and traction. A separate insole may also be included (e.g., within the upper 102). Suitable polymer foam materials for at least portions of the midsole 108 include ethylvinylacetate (“EVA”) or polyurethane (“PU”) that compress resiliently under an applied load to attenuate ground reaction forces.
For example, some footwear users participate in events or exercise programs that require frequent direction changes, often at high speeds. Such direction changes typically require the athlete to solidly plant and then push off one foot in a sideways direction, at times with some amount of twisting or spinning action. During these and other types of events, a user's foot can experience significant forces and motions. Designing footwear to support and/or protect the foot during such activities remains an ongoing challenge.